Low alloy steel of high yield strength



90,000 p. S. l.

Patented Apr. 7, 1953 LOW ALLOY STEEL OF HIGH YIEL STRENGTH Peter Payson, New York, N. Y., and Alvin E.

Nehrenberg, Bloomfield, N. J., assignors to Crucible Steel Company of America, New York, N. Y., a corporation of New Jersey jNo Drawing. Application August 17, 1950, Serial No. 180,090

This invention pertains to a relatively low alloy steel of exceptionally high yield strength.

. :It is an object of the invention to provide a readily weldablelow carbon, low alloy steel which in the as rolled, or normalized, condition has a minimum yield strength (at 0.2% offset) of about There are many'high strength, low alloy structural steels being marketed at present which as rolled have nominal yield strengths-of about 50,000 p. s. i. and a few of these in the as rolled condition have yield strengths as high as 70,000 p. s. i. but none so far as we know has the desired combination of good weldability, relatively low alloy content, and yield strength of 90,000

p. s. i. or more, as provided by the steel of our invention. It is obvious that higher yield strength in the steel makes for lighter weight .construction which is especially desirable for mobile equipment such as railroad cars, automobiles, buses, trucks, aircraft, steam shovels, derrick booms, gun carriages, and thelike, as well as for heavy stationary structures such as bridges and hangars in which a considerable part of the "steel used is necessary to support the weight of the steel itself.

Ordinary low carbon steel, as cooled in air has a structure of ferrite and pearlite which is quite weak. Furthermore, the ordinary low carbon steel .cannot be strengthenedvery much even by 3Claims. (0175-125) alloying elements, and that it is preferable to use a number of alloying elements instead of one or two. The common alloying elements which are most-effective for increasing hardenability are manganese, molybdenum and chromium, in that order. Since manganese is the most effective and least expensive of these elements we use a minimum of 1.0% of manganese in our steel and may use as much as 2.0% manganese. Since molybdenum is much more expensive than manganese we use a smaller amount from about .05 to .60% of this element in our steel. Chromium is used up to about 1.2%, although generally we limit this element to about 0.80%.

As is well known, it is desirable that the high strength low alloy steels should be more rust resistant than ordinary carbon steel and for this purpose we add about 0.20 to 0.60% copper to our steel.

In order to assure good weldability in the steel of our invention, we limit the carbon to 0.15% maximum and to assure good strength we set the carbon minimum at 05%, although we generally -aim to get between .08 and .15% carbon inthe steel.

Now we have discovered that a steel as outlined above but with further additions of silicon and nickel has a very high yield strength in the as rolled, or normalized, or stress relieved conditions heat treatment because of the very rapid trans- 30 as shown by the data below.

TABLE I Efiect of silicon on yield strength and ductility ,formation of the austenite of such steel during a water quench. For example, Sisco in Alloys of "Iron and Carbon, page 195, shows that low carbon steel as water quenched and tempered at 1000 F. has a yield strength of only 62,000 p. s. i.

i' It is well known that the transformation of .austenite can be retarded, that is, the hardenability of the "steel can beincreased, by use of It will be noted that in the first two steels of Table I all elements are the same except silicon and the steel with 0.91% silicon has a much better yield strength than the one with only 0.38 silicon. Also, in the last two steels of this group all elements are nearly thesame except silicon,

and of these two, the one with 1.61 silicon has a very much better yield strength than the steel cknesses tested s relief treatment As Air Cooled from 1725 1750 F., 111 rd.

steels which are nearly alike except for nickel. bar 5460 with 1.03% Ni has a yield strength 01' only 70,000 p. s. i. whereas bar 5461 with 1.77%

TABLE H Analysis, Percent The effect of nickel is shown in Table II.

Effect of nickel on yield strength and ductility Bar with 0.84 silicon. On the basis of these data we set the silicon limits for our steel at 0.90 to 2.0%.

1 mm e m mm .m m mmmw w m m u mww 1.... mmmmm 1 n 1 11 i 9H 1 r2 2 M1 m M sw mm c 1 as so D U e C O 8 M2 6 n 1 011% h aw E p r we 0 5 0445 s 0 248 r 0 O C n i 1 0000 m 0 m m OFJQMAMZ. 3m w m w 1% d mmmm m 1 vfl. r M m 6 6 W S O W n r rm 50 3 2 t m .m u N 9M 3 1% OY 9010 S m 0 67 fb r n A p 111 t h 9 0 e 0 h r 0 m .3. m t 0A7 00415 hh e w .1. 6 f hfl C 1 m w/L t S a b m m Mw 0 n n no! 3 mm 1 116 0 S e S 1 5 S 02 mmm rm. v fi m new at 11 r uH m m an m kcF N 111 m 00 005 n. imm s 11 m ww B m mmn n 0.1 e i t o 2 8 m b m .11 h 7764 t 5 0 841 N MM euu am vm t 4 401 W w n 446 '1 1 l 1 1 1 m GT :1 1. 0 g E O t S 111 00585 g O h n n a 0O 1 m 740862 m D E 0 & n I e m .1 %%M% mh L M 2 5% 3 902 100 .l h no I e e N 01b 35 5 S 12 Liane 212121 hdt a pn I e m 1111 t a a 7 W m 9m5 M. 11 H710 Tu e 111 MZH o a mw E s P 49 9 amT T N m 00265 E mwm mom L f. m 5 mwn dwd B m mmsas V .1 C O s 1111 d n T"! T 200 0 000000 3 "I. e S W" a S 111 N 26 mmwmmm .mrw he T m 1 wnnm m m m 0 11 at am ne m w p n s 38 sec m m I: Ynm. m S O S n l nf 0 0 h t 1.. .l .mhm m m wwwn m m2 u assess iasmAaa m P 88 mm one u: Swim G NW? W1 M Z1 P cs1 a m an a aw 1 I mm mm 0 576.02% t a S v tenet m 1111 fi. 3 u n m dmz o h 0324 E n mmm M 0 1111 I eJ 02082 l o w w w w w d L mn .d m 1 A I: 556 zeleo I: a? aTERR m 3 1L "h .1 B h.. S n mmmm S 5552 P n M C It will be noted that the first steel in the group in Table II containing high Mn, high Si, high Cr,

tively low yield strength, about equivalent to that N found in commercial high strength low alloy steels. The next steel bar 5458 with about 0.5% Ni has a much higher yield strength, but the third steel with 1.0% Ni has about the same yield -"strength as the second. However, the fourth and Mo and Cu, but with very little Ni, has a relasteel, bar 5259, with 2.17% Ni has the exceedingly Data on sheet stock of several thi both as rolled and after a stres of 1 hour at 1100 F. are given below.

high yield strength for normalized steel of 103,500 p. s. i. andthis together with an elongation value of 17.8%. Again in a comparison of the last two TABLE V Mechanical pfoperties of sheets of several sizes of steel of this invention tested both as rolled and as stress relieved at 1100 F. for 1 hour To summarize, the invention comprises a low alloy, high strength steel characterized in having in the as rolled and normalized conditions, in sections up to about one inch, a minimum yield strength at 0.2% offset, of 90,000 pounds per square inch, said steel comprising, in accordance with a broad range of analysis, about: 0.05 to 0.15% carbon; 1 to 2% manganese; 0.9 to 2% silicon; 1.5 to 2.5% nickel; chromium up to 1.2%; 0.05 to 0.6% molybdenum; 0.2 to 0.6% copper; up to 0.05% maximum, each of sulphur and phosphorus; and the balance substantially all iron, 1. e., iron except for the usual impurities within commercial tolerances.

A more preferred range of analysis comprises about: 0.08 to 0.15% carbon; 1.15 to 1.6% manganese; 1.2 to 1.8% silicon; 1.6 to 2.1% nickel; 0.5 to 1% chromium; 0.08 to 0.15% molybdenum; 0.25 to 0.5% copper; sulphur and phosphorus not to exceed 0.05% each, and the balance substantially all iron.

We claim:

1. A low alloy, high strength steel characterized in having in the as rolled and normalized conditions, in sections up to about one inch, a minimum yield strength at 0.2% offset of 90,000 pounds per square inch, said steel comprising about: 0.05 to 0.15% carbon; 1 to 2% manganese; 0.9 to 2% silicon; 1.5 to 2.5% nickel; 0.14 to 1.2% chromium; 0.05 to 0.6% molybdenum; 0.2 to 0.6% copper; up to 0.05% maximum, each of sulphur and phosphorus; and the balance iron.

2. A low alloy, high strength steel characterized in having in the as rolled and normalized conditions, in sections up to about one. inch, a minimum yield strength at 0.2% offset of 90,000 pounds per square inch, said steel comprising about: 0.08 to 0.15% carbon; 1.15 to 1.6% manganese; 1.2 to 1.8% silicon; 1.6 to 2.1% nickel; 0.5 to 1% chromium; 0.08 to 0.15% molybdenum; 0.25 to 0.5% copper; up to 0.05% maximum, each of sulphur and phosphorus; and the balance iron.

3. A low alloy, high strength steel characterized in having in the as rolled and normalized conditions, in sections up to about one inch, a

minimum yield strength at 0.2% ofiset of 90,000

pounds per square inch, said steel comprising about: 0.05 to 0.15% carbon; 1 to 2% manganese; 0.9 to 2% silicon; 1.5 to 2.5% nickel; 0.5 to 1.2% chromium; 0.05 to 0.6% molybdenum; 0.2 to 0.6% copper; up to 0.05% maximum, each of sulphur and phosphorus; and the balance iron.

PETER PAYSON. ALVIN E. NEHRENBERG.

REFERENCES CITED Thefollowing references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,447,089 Payson, et a1. Aug. 17, 1948 FOREIGN PATENTS Number Country Date 673,465 Germany Mar. 22, 1939 OTHER REFERENCES Alloys of Iron and Copper, page 168. Edited by Gregg and Danilofi. Published in 1934 by the Mo- Graw-Hill Book Co., New York.

Metal Progress, July 1935, page 29. Published by the American Society for Metals, Cleveland, Ohio. 

1. A LOW ALLOY, HIGH STRENGTH STEEL CHARACTERIZED IN HAVING IN THE AS ROLLED AND NORMALIZED CONDITIONS, IN SECTIONS UP TO ABOUT ONE INCH, A MINIMUM YIELD STRENGTH AT 0.2% OFFSET OF 90,000 POUNDS PER SQUARE INCH, SAID STEEL COMPRISING ABOUT: 0.05 TO 0.15% CARBON; 1 TO 2% MANGANESE; 0.9 TO 2% SILICON; 1.5 TO 2.5% NICKEL; 0.14 TO 1.2% CHROMIUM; 0.05 TO 0.6% MOLYBDENUM; 0.2 TO 0.6% COPPER; UP TO 0.05% MAXIMUM, EACH OF SULPHUR AND PHOSPHORUS; AND THE BALANCE IRON. 